Vehicle systems may include various vacuum consumption devices that are actuated using vacuum. These may include, for example, a brake booster and a purge canister. Vacuum used by these devices may be provided by a dedicated vacuum pump. In other embodiments, one or more aspirators (alternatively referred to as ejectors, venturi pumps, jet pumps, and eductors) may be coupled in the engine system that may harness engine airflow and use it to generate vacuum.
In yet another example embodiment shown by Bergbauer et al. in U.S. Pat. No. 8,261,716, a control bore is located in the wall of the intake such that when the throttle plate is at idle position, vacuum generated at the periphery of the throttle is used for a vacuum consumption device. Therein, the positioning of the throttle plate in an idle position provides a constriction at the throttle plate's periphery. The increasing flow of intake air through the constriction results in a venturi effect that generates a partial vacuum. The control bore is sited so as to utilize the partial vacuum for a vacuum consumption device.
The inventors herein have identified potential issues with the above approach. As an example, the vacuum generation potential of the throttle is limited. For example, a single control bore at one location in the intake, as shown in U.S. Pat. No. 8,261,716, is utilized by the vacuum consumption device even though vacuum may be generated at the entire periphery of the throttle. To use vacuum generated at the entire periphery of the throttle, more control bores may be needed in the intake passage. However, fabricating these control bores may result in significant modifications to the design of the intake passage which can increase related expenses.
In the approaches that use one or more aspirators to generate vacuum, additional expenses may be incurred because of individual parts that form the aspirator including nozzles, mixing and diffusion sections, and check valves. Further, at idle or low load conditions, it may be difficult to control the total air flow rate into the intake manifold since the flow rate is a combination of leakage flow from the throttle and airflow from the aspirator. Typically, an aspirator shut off valve (ASOV) may be included along with the aspirator to control airflow but with added cost. Further, installing aspirators in the intake can lead to constraints on space availability as well as packaging issues.
In one example, the issues described above may be addressed by a method for replenishing vacuum in a vacuum consumption device by flowing air through an annular venturi passage located between identically shaped upper and lower halves of a vacuum generating device. In this way, the vacuum generating device provides vacuum without electronic valves and/or actuators. As one example, air flows through one or more venturi passages of the vacuum generating device. Vacuum is supplied from a venturi passage, through a passage located in the upper half, to the vacuum consumption device. In one example, the vacuum generating device is located in an intake passage and the upper half is configured to slide to and away from the lower half. A position of the upper half is based on an engine operating condition. As an example, the upper half is spaced away from the lower half for higher engine loads and pressed against the lower half for lower/idle engine loads. Thus, the vacuum generating device may adjust intake air flow to an engine while simultaneously providing vacuum to the vacuum consumption device.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.